DESCRIPTION

The owner ID and group ID of the file named by path or referenced by fd
is changed as specified by the arguments owner and group. The owner of a
file may change the group to a group of which he or she is a member, but
the change owner capability is restricted to the super-user.
The chown() system call clears the set-user-id and set-group-id bits on
the file to prevent accidental or mischievous creation of set-user-id and
set-group-id programs if not executed by the super-user. The chown()
system call follows symbolic links to operate on the target of the link
rather than the link itself.
The fchown() system call is particularly useful when used in conjunction
with the file locking primitives (see flock(2)).
The lchown() system call is similar to chown() but does not follow
symbolic links.
The fchownat() system call is equivalent to the chown() and lchown()
except in the case where path specifies a relative path. In this case
the file to be changed is determined relative to the directory associated
with the file descriptor fd instead of the current working directory.
Values for flag are constructed by a bitwise-inclusive OR of flags from
the following list, defined in
AT_SYMLINK_NOFOLLOW
If path names a symbolic link, ownership of the symbolic link is
changed.
If fchownat() is passed the special value AT_FDCWD in the fd parameter,
the current working directory is used and the behavior is identical to a
call to chown() or lchown() respectively, depending on whether or not the
AT_SYMLINK_NOFOLLOW bit is set in the flag argument.
One of the owner or group id’s may be left unchanged by specifying it as
-1.

RETURNVALUES

Upon successful completion, the value 0 is returned; otherwise the
value -1 is returned and the global variable errno is set to indicate the
error.

ERRORS

The chown() and lchown() will fail and the file will be unchanged if:
[ENOTDIR] A component of the path prefix is not a directory.
[ENAMETOOLONG] A component of a pathname exceeded 255 characters, or
an entire path name exceeded 1023 characters.
[ENOENT] The named file does not exist.
[EACCES] Search permission is denied for a component of the
path prefix.
[ELOOP] Too many symbolic links were encountered in
translating the pathname.
[EPERM] The operation would change the ownership, but the
effective user ID is not the super-user.
[EPERM] The named file has its immutable or append-only flag
set, see the chflags(2) manual page for more
information.
[EROFS] The named file resides on a read-only file system.
[EFAULT] The path argument points outside the process’s
allocated address space.
[EIO] An I/O error occurred while reading from or writing to
the file system.
The fchown() system call will fail if:
[EBADF] The fd argument does not refer to a valid descriptor.
[EINVAL] The fd argument refers to a socket, not a file.
[EPERM] The effective user ID is not the super-user.
[EROFS] The named file resides on a read-only file system.
[EIO] An I/O error occurred while reading from or writing to
the file system.
In addition to the errors specified for chown() and lchown(), the
fchownat() system call may fail if:
[EBADF] The path argument does not specify an absolute path
and the fd argument is neither AT_FDCWD nor a valid
file descriptor open for searching.
[EINVAL] The value of the flag argument is not valid.
[ENOTDIR] The path argument is not an absolute path and fd is
neither AT_FDCWD nor a file descriptor associated with
a directory.

SEEALSO

STANDARDS

The chown() system call is expected to conform to ISO/IEC 9945-1:1990
(“POSIX.1”). The fchownat() system call follows The Open Group Extended
API Set 2 specification.

HISTORY

The chown() function appeared in Version 7 AT&T UNIX. The fchown()
system call appeared in 4.2BSD.
The chown() system call was changed to follow symbolic links in 4.4BSD.
The lchown() system call was added in FreeBSD 3.0 to compensate for the
loss of functionality.
The fchownat() system call appeared in FreeBSD 8.0.